PNAS – Proceedings of the National Academy of Sciences of the United States
December 21, 2021; vol. 118 no. 51
https://www.pnas.org/content/118/51

Global monitoring of the impact of the COVID-19 pandemic through online surveys sampled from the Facebook user base
Christina M. Astley, Gaurav Tuli, Kimberly A. Mc Cord, Emily L. Cohn, Benjamin Rader, Tanner J. Varrelman, Samantha L. Chiu, Xiaoyi Deng, Kathleen Stewart, Tamer H. Farag, Kristina M. Barkume, Sarah LaRocca, Katherine A. Morris, Frauke Kreuter, and John S. Brownstein
PNAS December 21, 2021 118 (51) e2111455118; https://doi.org/10.1073/pnas.2111455118